1. Technical Field
The present invention relates to a printing device and a printing method.
2. Background Technology
A technology for reproducing multi-gradation images has been used in a printing device such as a printer in which one or more types of dots are recorded on a printing medium. There have recently been remarkable advances in multi-gradation technologies, and the formation of so-called photographic quality images can now be realized by combining two sizes of multi-colored dots such as cyan (C), magenta (M), yellow (Y), and black (K) and controlling the distribution of these dots. When attempts are made to reproduce a multi-gradation image with high image quality using fewer gradation values such as by forming or not forming dots (turning dots ON/OFF), controlling the distribution of dots properly becomes a problem. Because of advances in technologies for analyzing the distribution of these dots in a spatial frequency range, image quality can now be improved by maintaining in the dot distribution noise characteristics where the number of components at or below a predetermined frequency is kept as low as possible in a spatial frequency range.
Blue noise characteristics are typical of these noise characteristics. Blue noise refers, for example, to characteristics in which the spatial frequencies of an image formed uniformly of dots for reproducing an image having a constant gradation value include substantially no components at or below a predetermined frequency. While the human eye is sensitive to low-frequency characteristics below a certain level, high-frequency components are not very visible. For this reason, images with these blue noise characteristics have a smooth, high-quality feel. A well-known image formation technology having these blue noise characteristics has been disclosed in Patent Citation 1.    U.S. Pat. No. 5,341,228 (Patent Document 1) is an example of the related art.